.real-world-example {
  background: radial-gradient(
      circle at left 0% bottom $position,
      transparent,
      transparent $diameter,
      #fbfbfb calc(#{$diameter} + 1px) // Add 1px for edge-smoothing.
    );
}

.simplification { 
  foo: (
    calc() // not a comment anymore
  );
}
